The invention generally relates to blood processing systems and methods. In a more specific sense, the invention relates to systems and methods for removing leukocytes from blood components collected for therapeutic purposes.
Today blood collection facilities routinely separate whole blood into its various therapeutic components, such as red blood cells, platelets, and plasma.
One separation technique that is in widespread use today uses a multiple blood bag system. The bag system includes a primary blood bag and one or more transfer bags, which are integrally connected to the primary bag by tubing. The technique collects from a donor a single unit (about 450 ml) of whole blood in the primary blood bag. The donor is then free to leave.
The donor""s whole blood later undergoes centrifugal separation within the primary bag into red blood cells and plasma rich in platelets. The plasma rich in platelets is expressed out of the primary bag into a transfer bag, leaving the red blood cells behind. The plasma rich in platelets then undergoes further centrifugal separation within the transfer bag into a concentration of platelets and plasma poor in platelets. The plasma poor in platelets is expressed from the transfer bag into another transfer bag, leaving the concentration of platelets behind.
Using multiple blood bag systems, all three major components of whole blood can be collected for therapeutic use. However, the yield for each component collected is limited to the volume of the components that are contained in a single unit of whole blood. Furthermore, because red blood cells are retained, United States governmental regulations prohibit collecting another unit of whole blood from the donor until six weeks later.
Certain therapies transfuse large volumes of a single blood component. For example, some patients undergoing chemotherapy require the transfusion of large numbers of platelets on a routine basis. Multiple blood bag systems simply are not an efficient way to collect these large numbers of platelets from individual donors.
On line blood separation systems are today used to collect large numbers of platelets to meet this demand. On line systems perform the separation steps necessary to separate concentration of platelets from whole blood in a sequential process with the donor present. On line systems establish a flow of whole blood from the donor, separate out the desired platelets from the flow, and return the remaining red blood cells and plasma to the donor, all in a sequential flow loop.
Large volumes of whole blood (for example, 2.0 liters) can be processed using an on line system. Due to the large processing volumes, large yields of concentrated platelets (for example, 4xc3x971011 platelets suspended in 200 ml of fluid) can be collected. Moreover, since the donor""s red blood cells are returned, the donor can donate whole blood for on line processing much more frequently than donors for processing in multiple blood bag systems.
Regardless of the separation technique used, when collecting blood components for transfusion, it is desirable to minimize the presence of impurities or other materials that may cause undesired side effects in the recipient. For example, because of possible febrile reactions, it is generally considered desirable to transfuse red blood cells and platelets that are substantially free of leukocytes, particularly for recipients who undergo frequent transfusions.
Several United States Patents are directed to the removal of leukocytes from red blood cells and platelet components in multiple blood bag systems. For example, see U.S. Pat. Nos. 4,767,541; 5,089,146; 5,100,564; and 5,128,048.
U.S. Pat. No. 5,427,695 is directed to the removal of leukocytes from platelet-rich plasma during on line blood processing.
The platelet-rich suspension product obtained using prior on line blood collection systems and methods may still lack the desired physiologic characteristics imposed by the end user (typically a blood bank or hospital) for long term storage and transfusion. For example, the platelet-rich suspension may include residual leukocytes that, while very small in relation to the leukocyte population in whole blood, are still greater than the leukocyte population standards desired by the end user.
Therefore, despite significant advances in blood processing technology, a need still exists for further improved systems and methods for removing undesired matter like leukocytes from blood components in a way that lends itself to use in high volume, on line blood collection environments.
The invention provides on line blood processing systems and methods for obtaining a finished platelet suspension having a desired physiologic characteristic. In a preferred embodiment, the desired physiologic characteristic comprises a desired reduced residual population of leukocytes.
The systems and methods that embody features of the invention establish on line communication between a container and a source of blood containing leukocytes and platelets, such as a human donor. The systems and methods create a centrifugal field between the source of blood and the container. The centrifugal field separates from the blood an unfinished suspension of platelets having a first physiologic characteristic different than the desired physiologic characteristic. In a preferred embodiment, the unfinished platelet suspension contains an initial leukocyte population greater than the desired residual leukocyte population.
According to the invention, the systems and methods pump the unfinished platelet suspension outside the centrifugal field through a finishing device. The finishing device changes the first physiologic characteristic to the desired physiological characteristic, thereby creating the finished platelet suspension. In a preferred embodiment, the finishing device reduces the leukocyte population by filtration. The systems and methods convey the finished platelet suspension from the finishing device directly into the container for storage or transfusion.
The systems and methods that embody the features of the invention function without interrupting the on line communication between the container and the source of blood.
Other features and advantages of the invention can be found in the drawings, accompanying description, and claims of this Specification.